[Solved] PdfViewerToolbar UI for WPF

private void toolbar_Loaded(object sender, RoutedEventArgs e)
{
	var toolBar = this.pdfToolBar.FindChildByType<RadToolBar>();
	var button = new RadButton()
	{
		Content = "Custom button",
		Background = Brushes.Red,
		HorizontalAlignment = HorizontalAlignment.Left,
		VerticalAlignment = VerticalAlignment.Stretch,
		Margin = new Thickness(2),
		Padding = new Thickness(0),
		HorizontalContentAlignment = HorizontalAlignment.Stretch,
		VerticalContentAlignment = VerticalAlignment.Center,
		IsBackgroundVisible = false
	};
	button.Click += Button_Click;
	toolBar.Items.Add(button);
}